Solid state circuit interrupter

ABSTRACT

A circuit interrupter including a current sensor having a normal sensor output and an over current detection output, a solid state switch module structured to have a closed state to allow current to flow through the circuit interrupter and an open state to interrupt current flowing through the circuit interrupter, a gate driver structured to control the solid state switch module including a desaturation function output, wherein the gate driver is structured to cause the solid state switch module to interrupt current flowing through the circuit interrupter when the DESAT function output changes to the on state, and an electronic trip circuit structured to output a trip signal to the gate driver when the normal sensor output reaches a first threshold level or the overcurrent detection output changes to the on state.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of, and claims priority under 35U.S.C. § 120 from, U.S. patent application Ser. No. 16/775,985, filedJan. 29, 2020, entitled “SOLID STATE CIRCUIT INTERRUPTER”, the contentsof which are incorporated herein by reference.

This application is related to commonly assigned U.S. patent applicationSer. No. 16/775,976, filed Jan. 29, 2020, now issued as U.S. Pat. No.11,239,649, issued Feb. 1, 2022, entitled “SOLID STATE CIRCUITINTERRUPTER” and commonly assigned U.S. patent application Ser. No.17/516,941, filed Nov. 2, 2021, entitled “SOLID STATE CIRCUITINTERRUPTER”.

BACKGROUND Field

The disclosed concept relates generally to circuit interrupters, and inparticular, to solid state circuit interrupters.

Background Information

Circuit interrupters, such as for example and without limitation,circuit breakers, are typically used to protect electrical circuitryfrom damage due to an overcurrent condition, such as an overloadcondition, a short circuit, or another fault condition, such as an arcfault or a ground fault. Solid state circuit interrupters use solidstate components, e.g., semiconductor devices, to switch on and offcurrent flowing from a power source to a load.

Solid state circuit interrupters provide faster tripping thanconventional mechanical circuit interrupters. However, thesecapabilities have not been optimally utilized. Additionally, solid statecircuit interrupters provide different safety and wellness concerns thanconventional mechanical circuit interrupters. There is considerable roomfor improvement in solid state circuit interrupters.

SUMMARY

In accordance with an aspect of the disclosed concept, a circuitinterrupter structured to electrically connect between a power sourceand a load comprises: a current sensor structured to sense currentflowing through the circuit interrupter and having a normal sensoroutput proportional to the current flowing through the circuitinterrupter and an over current detection (OCD) output that changes toan on state when the current flowing through the circuit interrupterreaches a second threshold level; a solid state switch module structuredto have a closed state to allow current to flow through the circuitinterrupter and an open state to interrupt current flowing through thecircuit interrupter; a gate driver structured to control the solid stateswitch module to interrupt current flowing through the circuitinterrupter, wherein the gate driver includes a desaturation (DESAT)function output that changes to an on state when the current flowingthrough the circuit interrupter reaches a third threshold level, andwherein the gate driver is structured to cause the solid state switchmodule to interrupt current flowing through the circuit interrupter whenthe DESAT function output changes to the on state; and an analog tripcircuit structured to receive the normal sensor output and the OCDoutput and to output a trip signal to the gate driver when the normalsensor output reaches a first threshold level or the OCD output changesto the on state, wherein the trip signal causes the gate driver tocontrol the solid state switch module to interrupt current flowingthrough the circuit interrupter.

In accordance with an aspect of the disclosed concept, a circuitinterrupter structured to electrically connect between a power sourceand a load comprises: separable contacts structured to open to providegalvanic isolation between the power source and the load; an operatingmechanism structured to open and close the separable contacts; a firstposition sensor structured to sense a position of the separablecontacts; a solid state switch module structured to have a closed stateto allow current to flow through the circuit interrupter and an openstate to interrupt current flowing through the circuit interrupter; andan electronic trip unit structured to control the solid state switchmodule to change between the open state and the closed state and tocontrol the operating mechanism to open the separable contacts, wherein,based on an output of the first position sensor, the electronic tripunit is structured to control the solid state switch module to controlthe solid state switch module to change from the open state to theclosed state when the separable contacts are in a closed position.

In accordance with an aspect of the disclosed concept, a solid stateswitch assembly for use in a circuit interrupter comprises: an inputterminal; a first conductor; an output terminal; a second conductor; asolid state switch module electrically connected to the input terminalwith the first conductor and electrically connected to the outputterminal with the second conductor and including at least one solidstate switch; a heat sink attached to the solid state switch module; acurrent sensor structured to sense current flowing through the solidstate switch module; and a number of metal oxide varistors (MOVs).

In accordance with an aspect of the disclosed concept, a circuitinterrupter comprises: a frame including a number of compartments; and anumber of solid state switch assemblies, each solid state switchassembly disposed in a corresponding one of the number of compartmentsand including: an input terminal; a first conductor; an output terminal;a second conductor; a solid state switch module electrically connectedto the input terminal with the first conductor and electricallyconnected to the output terminal with the second conductor and includingat least one solid state switch; a heat sink; a current sensorstructured to sense current flowing through the solid state; and anumber of metal oxide varistors (MOVs).

In accordance with an aspect of the disclosed concept, a method ofoperating a circuit interrupter having a solid state switch moduleincluding a solid state switch comprises: monitoring a characteristic ofthe solid state switch; determining that the characteristic of the solidstate switch meets or exceeds a predetermined threshold; and providingan indication in response to determining that the characteristic of thesolid state switch meets or exceeds the predetermined threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a circuit interrupter in accordancewith an example embodiment of the disclosed concept;

FIG. 2 is a circuit diagram of a power supply in accordance with anexample embodiment of the disclosed concept;

FIGS. 3A and 3B are a circuit diagram of an analog trip circuit inaccordance with an example embodiment of the disclosed concept;

FIGS. 4A and 4B are a circuit diagram of a gate driver circuit inaccordance with an example embodiment of the disclosed concept;

FIGS. 5A and 5B are partial assembly views of a circuit interrupter inaccordance with an example embodiment of the disclosed concept;

FIGS. 6A and 6B are partial assembly views of a circuit interrupter inaccordance with an example embodiment of the disclosed concept;

FIG. 7 is a view of a partially disassemble circuit interrupter inaccordance with an example embodiment of the disclosed concept;

FIG. 8 is a partial internal side view of a circuit interrupter inaccordance with an example embodiment of the disclosed concept;

FIGS. 9A-C are views of a solid state switch assembly in accordance withan example embodiment of the disclosed concept;

FIGS. 10A-D are views of a heat sink and solid state switch module inaccordance with an example embodiment of the disclosed concept;

FIGS. 11A-B are views of a frame housing solid state switch assembliesin accordance with an example embodiment of the disclosed concept; and

FIG. 12 is a flowchart of a method of operating a circuit interrupter inaccordance with an example embodiment of the disclosed concept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Directional phrases used herein, such as, for example, left, right,front, back, top, bottom and derivatives thereof, relate to theorientation of the elements shown in the drawings and are not limitingupon the claims unless expressly recited therein.

As employed herein, the statement that two or more parts are “coupled”together shall mean that the parts are joined together either directlyor joined through one or more intermediate parts.

FIG. 1 is a schematic diagram of a circuit interrupter 10 (e.g., withoutlimitation, a circuit breaker) in accordance with an example embodimentof the disclosed concept. The circuit interrupter 10 in some exampleembodiments is a 100 A (I_(n)=100 A) rated device (i.e., rated currentI_(n) is 100 A). The circuit interrupter 10 is structured to beelectrically connected between a power source 2 and a load 4. Thecircuit interrupter 10 is structured to trip open or switch open tointerrupt current flowing to the load 4, for example, in the case of afault condition (e.g., without limitation, an overcurrent condition) toprotect the load 4, circuitry associated with the load 4, as well as thecomponents within the circuit interrupter 10.

The circuit interrupter 10 includes a solid state switch assembly 200including a solid state switch module 202 and a current sensor 206. Thecircuit interrupter 10 also includes a gate driver circuit 204 and ananalog trip circuit 208 associated with the solid state switch assembly200. The circuit interrupter 10 further includes an operating mechanism300, separable contacts 302, and an electronic trip unit 304, as well asa power supply 100. Additionally, the circuit interrupter 10 includespositon sensors 500, 502, 504, and close and open buttons 506,508. Itwill be appreciated by those having ordinary skill in the art that thecircuit interrupter 10 need not include all these components. Forexample, in example embodiments, the circuit interrupter 10 may onlyinclude a subset of these components without departing from the scope ofthe disclosed concept.

The circuit interrupter 10 is structured to provide solid state circuitinterruption via the solid state switch assembly 200 and galvanicisolation via the separable contacts 302. The solid state switch module202 includes one or more solid state switches (e.g., without limitation,metal-oxide-semiconductor field-effect transistors (MOSFETS),insulated-gate bipolar transistors (IGBTs), or other suitable types ofsolid state switches) electrically connected between the power source 2and the load 4. The solid state switch module 202 has a closed state inwhich power is allowed to flow through the solid state switch module 202between the power source 2 and the load 4 and an open state in whichpower is prevented from flowing between the power source 2 and the load4.

The gate driver circuit 204 is structured to control the state of thesolid state switch module 202. The gate driver circuit 204 has adesaturation function (DESAT) that changes from an off state to an onstate when current flowing through the solid state switch module 202reaches a predetermined threshold level. In an example embodiment, thepredetermined threshold level is about 2250 A (22.5×I_(n)). The DESATfunction operates by monitoring a forward voltage drop of a solid stateswitch in the solid state switch module 202. When the forward voltagedrop reaches a threshold level, the DESAT function changes to the onstate and the gate driver circuit 204 responsively causes the solidstate switch module 202 to change to the open state, interruptingcurrent flowing through the circuit interrupter 10. In an exampleembodiment, the DESAT function has a threshold voltage of 9V. Based onthe on-resistance of a silicon-carbide (SiC) MOSFET, the forward voltagedrop will reach 9V when the current level is about 2250 A. Thus, theDESAT function will change to the on state when the current flowingthrough the solid state switch module 202 reaches about 2250 A. It willbe appreciated that these threshold values are merely provided as anexample. Different threshold values may be employed without departingfrom the scope of the disclosed concept.

Using the DESAT function of the gate driver circuit 204 to cause thesolid state switch module 202 to open allows for very fast interruptionof the current flowing through the circuit interrupter 10. In someexample embodiments of the disclosed concept, interruption based on theDESAT function can be within 0.5 microseconds. In some exampleembodiments of the disclosed concept, the gate driver circuit 204includes a capacitor structured to change the interruption based on theDESAT function. For example, the time to interrupt based on the DESATfunction is based on the capacitance of the capacitor. In this manner,the interruption time based on the DESAT function can be easily adjustedby changing the capacitor.

In some example embodiments, the current sensor 206 is structured toprovide a normal sensor output that is proportional to the currentflowing through the circuit interrupter 10 and an overcurrent detection(OCD) output that changes to an on state when the current flowingthrough the circuit interrupter 10 reaches a threshold level. In anexample embodiment, the current sensor 206 is a Hall-effect sensor.

The analog trip circuit 208 is structured to receive the normal sensoroutput and the OCD output from the current sensor 206. The analogcircuit 208 is electrically connected to the gate driver circuit 204 andis structured to output a trip signal to the gate driver circuit 204. Inresponse to the trip signal, the gate driver circuit 204 controls thesolid state switch module 202 to change to the open state, interruptingcurrent flowing through the circuit interrupter 10. The analog tripcircuit 208 is structured to output the trip signal in response to thenormal sensor output reaching a threshold level or the OCD outputchanging to the on state. The analog trip circuit 208 is structured tooutput the trip signal in response to the OCD output changing to the onstate within a first predetermined amount of time and to output the tripsignal in response to the normal sensor output reaching the thresholdlevel within a second predetermined amount of time. In an exampleembodiment, the first predetermined amount of time is less than thesecond predetermined amount of time. In an example embodiment, the firstpredetermined amount of time is 10 nanoseconds and the secondpredetermined amount of time is 100 nanoseconds. However, it will beappreciated that other predetermined amounts of time may be employedwithout departing from the scope of the disclosed concept. In an exampleembodiment, interruption of current flowing through the circuitinterrupter 10 based on the normal sensor output reaching the thresholdlevel occurs within 4 microseconds and interruption based on the OCDoutput occurs within 2 microseconds. However, it will be appreciatedthat these are example times and other times may be employed withoutdeparting from the scope of the disclosed concept. In some exampleembodiments, the threshold level associated with the normal currentsensor output is within a range of about 200 (2×I_(n)) to 750 A(7.5×I_(n)) and the threshold level associated with the OCD output isabout 750 A (7.5×I_(n)). However, it will be appreciated that these arejust example values and may be adjusted without departing from the scopeof the disclosed concept.

With the analog trip circuit 208 and the DESAT function of the gatedriver circuit 204, a three-level interruption logic is able to beemployed within the circuit interrupter 10. The DESAT function providesthe fastest interruption based on the highest current threshold, the OCDoutput provides the second fastest interruption based on the secondhighest current threshold, and the normal sensor output provides thethird fastest interruption based on the third highest current threshold.In an example embodiment, the highest current threshold is about 2250 A(22.5×I_(n)) and the fastest interruption is within 0.5 microseconds,the second highest current threshold is about 750 A (7.5×I_(n)) and thesecond fastest interruption is within 2.5 microseconds, and the thirdhighest current threshold is selected from within a range of about200(2×I_(n))−750 A (7.5×I_(n)) and the third fastest interruption iswithin 4 microseconds. With the analog trip circuit 208 and the DESATfunction of the gate driver circuit 204, interruption is able to occurfaster than through digital circuit protection, such as that provided bythe electronic trip unit 304.

In some example embodiments of the disclosed concept, the electronictrip unit 304 is also structured to output a trip signal to the gatedriver circuit 204 to cause the gate driver circuit 204 to control thesolid state switch module 202 to change to the open state. Theelectronic trip unit 304 may output the trip signal based on currentthresholds below the third highest current threshold associated withtrips based on the normal sensor output by the analog trip circuit 208.The electronic trip unit 304 may be structured to output the trip signalbased on an I-t trip curve such that when the electronic trip unit 304detects a fault condition based on the normal sensor output of thecurrent sensor 206, the electronic trip unit 304 will output the tripsignal to the gate driver circuit 204 at the time associated with thecurrent level based on the I-t trip curve.

The circuit interrupter 10 also includes the operating mechanism 300 andseparable contacts 302. The separable contacts 302 are structured toopen to provide galvanic isolation between the power source 2 and theload 4. The operating mechanism 300 is structured open and close theseparable contacts 302. For example, the operating mechanism 300 mayinclude a movable arm, which when moved causes the separable contacts302 to open or close. The electronic trip unit 304 is structured tocontrol the operating mechanism 300 to open the separable contacts 302.For example, the electronic trip unit 304 may be structured to controlthe operating mechanism 300 to open the separable contacts 302 onlyafter the solid state switch module 202 has changed to the open state.For example, in a mechanical circuit interrupter, the separable contactsare designed to interrupt current flowing through the circuitinterrupter and have associated components such as an arc chute tomanage arcing as a result of circuit interruption. The circuitinterrupter 10 is a solid state circuit interrupter in which current isinterrupted by the solid state switch module 202. The separable contacts302 need not be designed to interrupt the current and need not have anassociated arc chute or other components, as they are only intended toopen after the solid state switch module 202 has interrupted thecurrent. As such, the electronic trip unit 304 may be structured tocontrol the operating mechanism 300 to open the separable contacts 302only after the solid state switch module 202 has changed to the openstate. Similarly, the electronic trip unit 304 may be structured tocause the gate driver circuit 204 to change the solid state switchmodule 202 to the closed state only after the separable contacts 302 areclosed. In this manner, bounce arc due to bouncing of the separablecontacts 302 is prevented. In some example embodiments, the separablecontacts 302 are closed with manual intervention by a user through, forexample, a reset switch. In some example embodiments, the operatingmechanism 300 is structured to close the separable contacts 302 inresponse to a close signal from the electronic trip unit 304.

In some example embodiments of the disclosed concept, the circuitinterrupter 10 includes a position sensor 500. The position sensor 500is structured to sense whether the separable contacts 302 are in theopen position or the closed position. The output of the position sensor500 may be provided to the electronic trip unit 304. Based on the outputof the position sensor 500, the electronic trip unit 304 is able todetermine the position of the separable contacts 302. Similarly, theelectronic trip unit 304 unit may receive an output of the gate drivercircuit 204 indicative of the state of the solid state switch module202. With these outputs, the electronic trip unit 304 may ensure thatthe separable contacts 302 are opened only after the solid state switchmodule 202 has changed to the open state and that the solid state switchmodule 202 is changed to the closed state only after the separablecontacts 302 are closed.

In some example embodiments, the circuit interrupter 10 includes a closebutton 506 and an open button 508. It will be appreciated that buttonsare used as an example. It will be appreciated that any user actuatableelement may be employed without departing from the scope of thedisclosed concept. In an example embodiment, the electronic trip unit304 is structured to control the operating mechanism 300 to close theseparable contacts 302 to close and then output a close signal to thegate driver circuit 204 to cause the gate driver circuit 204 to changethe solid state switch module 202 to the closed state in response toactuation of the close button 506. In an example embodiment, theelectronic trip unit 304 is structured to output the trip signal to thegate driver circuit 204 to cause the gate driver circuit 204 to changethe solid state switch module 202 to the open state and then control theoperating mechanism 300 to open the separable contacts 302 in responseto actuation of the open button 508. In some example embodiments, aposition sensor 502 may be used to sense actuation of the close button506 and a position sensor 504 may be used to sense actuation of the openbutton 508. The electronic trip unit 304 may be structured to receiveoutputs of the position sensors 502,504 and sense actuation of the closeand open buttons 506,508 based on outputs of the position sensors502,504.

The position sensors 500,502,504 may be any suitable type of sensor forsensing the position of a component. As an example, the position sensors500,502,504 may be micro switches that are actuated by movement of theircorresponding component. For example, the position sensor 500 may be amicro switch disposed by a movable arm of the operating mechanism 300such that movement of the moveable arm to open or close the separablecontacts 302 actuates the position sensor 500, and based on the outputof the position sensor 500, the electronic trip unit 304 is able tosense the current position of the separable contacts 302. Similarly, theposition sensors 502,504 may be micro switches disposed such thatactuation of the on and off buttons 506,508, respectively, actuates theposition sensors 502,504.

The power supply 100 is structured to receive power from the powersource 2 and convert the power from the power source 2 to power usableby components of the circuit interrupter 10. For example, the powersupply 100 may convert alternating current power from the power source 2to direct current power usable by components of the circuit interrupter10. The power from the power supply 100 may provide power to operatecomponents such as, without limitation, the electronic trip unit 304,the gate driver circuit 204, the operating mechanism 300 (e.g., asolenoid included in the operating mechanism), the current sensor 206,and the analog trip circuit 208). The power supply 100 may generatedirect current power at multiple voltages (e.g., without limitation,24V, 15V, 5V, and 3.3V). In an example embodiment, the power supply 100may be omitted and power to operate the components of the circuitinterrupter 10 may be provided by an external power supply. In someexample embodiments, the electronic trip unit 304 is structured to causethe solid state switch module 202 to change to the open state and theseparable contacts 302 to open if power is unavailable from the powersupply 100 or an external power supply. In some example embodiments, thepower supply 100 is structured to use line-line voltage from the powersource 2 to generate the direct current power for use by the componentsof the circuit interrupter 10. For example, rather than being connectedbetween line and neutral conductors, the power supply 100 is insteadconnected between multiple line conductors. While FIG. 1 shows a singlepole of the circuit interrupter 10, it will be appreciated that thecircuit interrupter 10 may have multiple poles in which multiple linephases of power flow through the circuit interrupter 10 with the powersupply 100 being connected to the multiple line phases.

FIG. 2 is a circuit diagram of the power supply 100 in accordance withan example embodiment of the disclosed concept. In this exampleembodiment, the power supply 100 includes a three-phase line input 110,a rectifier diode bridge 120, a filtering circuit 130, a DC/DC converter140, and an output 150. The three-phase line input 110 receives powerfrom multiple lines phases and provides a line-to-line AC voltage inputto the rectifier diode bridge 120. The rectifier diode bridge 120converts the AC voltage to DC voltage and outputs the DC voltage intothe filtering circuit 130. The filtering circuit 130 limits the currentinput, thereby protecting the power supply circuit 100 from rushing inof the current input, and filters the DC voltage via the currentdividers (C10, C11, C12, C13, R1, R2, R3, and R4). The DC/DC converter140 receives the filtered DC voltage from the filtering circuit 130 andconverts the filtered high DC voltage to low DC voltage, e.g., 24V, 15V,5V, or 3.3V. The DC/DC converter 140 then outputs the low DC voltage toprovide power for components of the circuit interrupter 10. The linevoltage is stepped down to, e.g., 24, 15, 5, or 3.3V DC, to fulfill thevoltage requirements of the electrical components of the circuitinterrupter 10. When the line to line voltage is not available, anexternal 24V power supply may be used. If there is neither the externalpower nor the line to line voltage, the solid state switch module 202may be changed to the open state. While FIG. 2 illustrates an example ofcircuitry used within the power supply 400, it will be appreciated thatFIG. 2 is merely an example embodiment. Circuit components may berearranged, added to, subtracted from, or implemented differentlywithout departing from the scope of the disclosed concept.

FIGS. 3A and 3B are a circuit diagram of the analog trip circuit 208 inaccordance with an example embodiment of the disclosed concept. Theanalog trip circuit 208 includes a normal sensor input 210 and an OCDinput 212. The normal sensor input 210 is structured to receive thenormal sensor output of the current sensor 206, which is proportional tocurrent flowing through the circuit interrupter 10. The OCD input 212 isstructured to receive the OCD output of the current sensor 206. Theanalog trip circuit 208 also includes a trip signal output 214 that iselectrically connected to the gate driver circuit 204. In response tothe normal sensor output reaching a threshold level or the OCD outputchanging to an on state, the analog trip circuit 208 is structured tooutput the trip signal at the output 214. The analog trip circuit 208 isstructured to compare the normal sensor output to the threshold levelwhile the OCD output is not needed to be compared to the thresholdlevel. By bypassing this check with the OCD output, the analog tripcircuit 208 is able to output the trip signal based on the OCD outputfaster than the trip signal based on the normal sensor output. FIGS. 3Aand 3B illustrates an example of logic circuitry used in the analog tripcircuit 208. However, it will be appreciated that the example shown inFIGS. 3A and 3B is merely an example implementation of the analog tripcircuit 208. It will be appreciated that the circuit components may berearranged, added to, subtracted from, or implemented differentlywithout departing from the scope of the disclosed concept.

FIGS. 4A and 4B are a circuit diagram of the gate driver circuit 204 inaccordance with an example embodiment of the disclosed concept. The gatedriver circuit 204 includes an enable input 216 and a DESAT input 222.The gate driver circuit 204 also includes a driver output 224 and faultoutput 218. The gate driver circuit 204 further includes a driver 220and a capacitor 226. The enable input 216 is electrically connected tothe analog trip circuit 208 and the electronic trip unit 304. The driveroutput 224 and the DESAT input 222 are electrically connected to thesolid state switch module 202. The fault output 218 is electricallyconnected to the electronic trip unit 218. The solid state switch module202 is structured to change between the open state and the closed statebased on the driver output 224. The driver 220 is structured to controlthe state of the driver output 224 based on the trip signal received atthe enable input 216 or the DESAT input 222. The driver 220 isstructured to implement the DESAT function based on the DESAT input 222.The timing associated with changing the driver output 224 based on theDESAT input 222 is based in part on the capacitance of the capacitor226. The driver 220 is also structured to control the state of the faultoutput 218 such that the electronic trip unit 304 may be notified whenthe gate driver circuit 204 has controlled the solid state switch module202 to change to the open or closed state. It will be appreciated thatthe example shown in FIGS. 4A and 4B is merely an example implementationof the gate driver circuit 204. It will be appreciated that the circuitcomponents may be rearranged, added to, subtracted from, or implementeddifferently without departing from the scope of the disclosed concept.

FIGS. 5A and 5B are partial assembly views of the circuit interrupter 10in accordance with an example embodiment of the disclosed concept. FIGS.5A and 5B show an example of the close and open buttons 506,508, theposition sensors 502,504, part of the operating mechanism 300, and partof the separable contacts 302. In the example shown in FIGS. 5A and 5B,a three pole operating mechanism 300 is shown with movable rotary armsthat move the separable contacts 302 in conjunction. The positionsensors 502,504 are associated with the close and open buttons 506,508,respectively, such that actuation of the on and off buttons 506,508causes actuation of the position sensors 502,504. For example,protrusions are attached to the on and off buttons 506,508 and move inconjunction with actuation of the close and open buttons 506,508. As anexample, the protrusion associated with the on button 508 may moveagainst the position sensor 504 when the close button 508 is actuated.FIGS. 5A and 5B show part of the separable contacts 302. In particular,FIGS. 5A and 5B show the moveable contact of the separable contacts 302.It will be appreciated that a stationary contact is associated with themoveable contact. Moving the moveable contact away from the stationarycontact opens the separable contacts 302.

FIGS. 6A and 6B are partial assembly views of the circuit interrupter 10in accordance with an example embodiment of the disclosed concept. FIG.6A shows part of the operating mechanism 300 and the separable contacts302 in the closed position. FIG. 6B shows part of the operatingmechanism and the separable contacts 302 in the open position. FIGS. 6Aand 6B also show the position sensor 500 which is structured to sensewhether the separable contacts 302 are in the closed or open position.The position sensor 500 may be associated with part of a moveable arm ofthe operating mechanism 300 such that the moveable arm abuts against theposition sensor when the separable contacts 302 are in the closedposition and moves away from the positon sensor 500 when the separablecontacts 302 are in the open position.

FIG. 7 is a partially disassembled elevation view of the circuitinterrupter 10 in accordance with an example embodiment of the disclosedconcept. FIG. 7 shows the close and open buttons 506,508, as well as astatus indicator 510 that indicates the position of the separablecontacts 302 in accordance with an example embodiment of the disclosedconcept.

FIG. 8 is a partial internal side view of the circuit interrupter 10 inaccordance with an example embodiment of the disclosed concept. Acurrent path 600 through the circuit interrupter is designated witharrows. As shown in FIG. 8 , current flowing through the circuitinterrupter 10 from the power source 2 first flows through the separablecontacts 302. The current then continues through the solid state switchassembly 200 and the current sensor 206 disposed proximate the output ofthe solid state switch assembly 200, where it is then provided to theload 4.

FIGS. 9A-C are views of the solid state switch assembly 200 inaccordance with an example embodiment of the disclosed concept. Thesolid state switch assembly 200 includes the solid state switch module202 and the current sensor 206. The solid state switch assembly 200 alsoincludes an input terminal 250 and an input conductor 252. The inputterminal 250 is structured to receive power from the power source 2 viathe separable contacts 302 and provide it to the solid state switchmodule 202 via the input conductor 252. The solid state switch assembly200 also includes an output terminal 256 and an output conductor 254.When the solid state switch module 202 is in the closed state, powerflows through the solid state switch module 202 to the load conductor254 and subsequently to the output terminal 256. The output terminal 256is structured to be electrically connected to the load 4. The solidstate switch assembly 200 also includes a module cover 258.

In FIG. 9C, the module cover 258 is omitted. The solid state switchassembly 200 also includes MOVs 262, shown in FIG. 9C, that are coveredby the module cover 258.

The solid state switch assembly 200 further includes a heat sink 260.The heat sink 260 is attached to the solid state switch module 200 andis described further with respect to FIGS. 10A-D.

FIGS. 10A and 10B are views of the heat sink 260 in accordance with anexample embodiment of the disclosed concept and FIGS. 10C and 10D areviews of the solid state switch module 202 attached to the heat sink 260in accordance with an example embodiment of the disclosed concept. Theheat sink 260 includes a first planar member 264 and a second planermember 268 that extends from one side of the first planar member 268.The heat sink 260 also includes multiple prongs 270 that extend from anopposite side of the first planar member 264.

The solid state switch member 202 is structured to attach to the secondplanar member 268, as shown in FIGS. 10C and 10D. In an exampleembodiment, fasteners 272 may be used to attach the solid state switchmember 202 to the second planar member 268. The heat sink 260 may becomposed of a metallic material and is operable to dissipate heatgenerated by the solid state switch module 202.

FIGS. 11A and 11B are views of a frame 280 for housing the solid stateswitch assemblies 200 in accordance with an example embodiment of thedisclosed concept. The frame 280 includes compartments 282, each housingone solid state switch assembly 200. In the example embodiment shown inFIGS. 11A and 11B, the frame 280 includes three compartments 282 andhouses three solid state switch assemblies 200. Each solid state switchassembly 200 may correspond to a pole of the circuit interrupter 10. Theframe 280 is thus suitable for use in a 3-pole circuit interrupter.However, it will be appreciated that the frame 280 may be modified tohave a different number of compartments 282 without departing from thescope of the disclosed concept.

The solid state switch assembly 200 has a modular design. Components ofthe solid state switch assembly 200 may be substituted for other similarshaped components depending on the application of the solid state switchassembly 200. For example, the solid state switch module 202 may besubstituted with another solid state switch module 202 for anapplication with different voltage and current requirements. Theremaining components of the solid state switch assembly 200 may remainunchanged, thus allowing a wider application of the solid state switchassembly 200 without the need to redesign the whole solid state switchassembly 200. Similarly, the current sensor 206 may be replaced withanother current sensor 206 in applications with different currentrequirements. Similarly, the other components of the solid state switchassembly 200 may be replaced.

FIG. 12 is a flowchart of a method of operating a circuit interrupter inaccordance with an example embodiment of the disclosed concept. Themethod may be implemented, for example, in the circuit interrupter 10described herein. Solid state circuit interrupters, such as the circuitinterrupter 10, present new concerns regarding health and remaining lifecompared to mechanical circuit interrupters. For example, monitoring thehealth of solid state switches differs from monitoring the health ofmechanical switches. However, in both cases, it is important to monitorwhen the switch is reaching the end of its lifespan and becomes at riskof failure.

The method of FIG. 12 begins at 700 with monitoring a characteristic ofthe solid state switch assembly 200. In some example embodiments, asolid state switch the solid state switch module 202 is monitored. Insome example embodiments, the MOVs 262 are monitored. It will beappreciated that both may be monitored. The monitored characteristic maybe a junction temperature, a forward volt drop (in the case of an IGBTsolid state switch), a body diode forward volt drop (in the case of aMOSFET solid state switch), a gate threshold voltage (in the case of aMOSFET solid state switch), or a gate leakage current (in the case of aMOSFET solid state switch) of the solid state switch. The monitoredcharacteristic may also be a voltage across the MOVs 262.

At 702, it is determined whether the monitored characteristic exceeds athreshold level. The threshold level may be selected based on themonitored characteristic and the device being monitored. In the case ofthe voltage across the MOVs 262, the threshold may be a time-varyingrange. For example, the voltage across the MOVs 262 may be monitored fora period of time after the solid state switch is opened. The thresholdrange changes over the period of time and it is determined whether thevoltage across the MOVs 262 goes outside that threshold range at aparticular time. If the characteristic does not exceed the thresholdlevel, the method returns to 700. However, if the characteristic exceedsthe threshold level, the method proceeds to 704.

At 704, an indication is provided. The indication may be via a displayon the circuit interrupter 10 or any other suitable type of indicationsuch as for example, an LED indicator, a wired or wireless communicationto an external device, etc. The indication notifies a user or technicianthat the component needs to be serviced or replaced. It will beappreciated that additional method steps may be employed such asservicing or replacing a component or controlling the circuitinterrupter 10 to trip open in response to determining that themonitored characteristic exceeds the threshold level.

The junction temperature is an indicator of the wellness of a solidstate switch. As an example, some solid state switches should be keptunder a threshold junction temperature of 150 degrees Celsius. If thejunction temperature reaches this threshold, then the solid state switchmay become damaged and fail. Thus, junction temperature of the solidstate switch is a useful characteristic to monitor.

The forward volt drop or body diode forward volt drop are alsoindicators of the wellness of a solid state switch. When the forwardvolt drop or body diode forward volt drop reach its threshold whenoperating at rated current, the solid state switch can become damagedand fail. The forward volt drop or body diode forward volt drop can becaused by a number of factors such as high current, bad heat conduction,or bad thermal management. Thus, the forward volt drop and body diodeforward volt drop are useful characteristics to monitor.

The gate threshold voltage or gate leakage current are also usefulcharacteristics of the solid state switch to monitor. The gate thresholdvoltage or gate leakage current exceeding their threshold levels candamage or cause the solid state switch to fail. The gate leakage currentis more sensitive to degradation of the solid state switch and ispossible to monitor while the solid state switch is closed andconducting current, which makes it more practical to monitor than thegate threshold voltage. However, both the gate threshold voltage andgate leakage current are useful characteristics to monitor to determinethe wellness of the solid state switch.

When the MOVs 262 begin to degrade, the voltage across the MOVs 262 willincrease or decrease. The MOVs 262 clamp voltage in a period of timeafter the solid state switch is opened, and thus this is the relevanttime period to monitor the voltage across the MOVs 262. An examplethreshold range may be ±10% of the MOVs 262 normal clamp voltage. Forexample, voltage across the MOVs 262 drifting more than 10% from theirnormal clamp voltage is an indication that the MOVs 262 are degradingand should be serviced or replaced. Thus, the voltage across the MOVs262 is another useful characteristic to monitor.

While some examples of characteristics to monitor have been described,it will be appreciated that other characteristics may be monitoredwithout departing from the scope of the disclosed concept. It will alsobe appreciated that additional action in addition to or in place ofproviding an indication may be performed in response to a characteristicexceeding its threshold.

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof.

What is claimed is:
 1. A circuit interrupter comprising: a frameincluding a number of compartments; a number of solid state switchassemblies, each solid state switch assembly disposed in a correspondingone of the number of compartments and including: an input terminal; afirst conductor; an output terminal; a second conductor; and a solidstate switch module electrically connected to the input terminal withthe first conductor and electrically connected to the output terminalwith the second conductor and including at least one solid state switchand a sensor structured to monitor a characteristic of the at least onesolid state switch during operation; and a controller coupled to thesensor and structured to at least determine whether the monitoredcharacteristic meets a predetermined threshold, and to cause the circuitinterrupter to trip open in response to a determination that themonitored characteristic has met the predetermined threshold, whereinthe at least one solid state switch comprises an insulated-gate bipolartransistor, and wherein the monitored characteristic comprises a forwardvolt drop of the IGBT and the predetermined threshold is met based onthe forward volt drop reaching a threshold voltage.
 2. The circuitinterrupter of claim 1, wherein the monitored characteristic comprises ajunction temperature of the IGBT, and the predetermined threshold is metbased on the junction temperature reaching a threshold temperaturecomprising 150 degrees Celsius.
 3. The circuit interrupter of claim 1,further comprising an indication mechanism structured to indicate thatthe monitored characteristic has met the predetermined threshold, theindication mechanism including at least one of a display, an LEDindicator, or a communication mechanism structured to communicate withan external device.
 4. The circuit interrupter of claim 3, wherein theindication mechanism is further structured to notify a user that the atleast one solid state switch needs to be serviced or replaced.
 5. Asolid state switch assembly for use in a circuit interrupter, the solidstate switch assembly comprising: an input terminal; a first conductor;an output terminal; a second conductor; and a solid state switch moduleelectrically connected to the input terminal with the first conductorand electrically connected to the output terminal with the secondconductor and including at least one solid state switch and a sensorstructured to monitor a characteristic of the at least one solid stateswitch during operation, the sensor coupled to a controller in thecircuit interrupter, wherein the controller is structured to, at least,determine whether the monitored characteristic meets a predeterminedthreshold, and cause the circuit interrupter to trip open in response toa determination that the monitored characteristic has met thepredetermined threshold, wherein the at least one solid state switchcomprises an insulated-gate bipolar transistor, and wherein themonitored characteristic comprises a forward volt drop of the IGBT andthe predetermined threshold is met based on the forward volt dropreaching a threshold voltage.
 6. The solid state switch assembly ofclaim 5, wherein the monitored characteristic further comprises ajunction temperature of the IGBT.
 7. The solid state switch assembly ofclaim 5, wherein the controller is coupled to an indication mechanism ofthe circuit interrupter, the indication mechanism structured to providean indication that the predetermined threshold has been met via adisplay, an LED indicator or a communication mechanism structured tocommunicate with an external device.
 8. The solid state switch assemblyof claim 7, wherein the indication mechanism is further structured tonotify a user that the at least one solid state switch needs to beserviced or replaced.
 9. A method of monitoring wellness of a solidstate switch integrated in a circuit interrupter, the method comprising:monitoring a characteristic of the solid state switch; determining thatthe monitored characteristic of the solid state switch meets apredetermined threshold; and tripping the circuit interrupter inresponse to determining that the monitored characteristic of the solidstate switch has met the predetermined level, wherein the solid stateswitch comprises an insulated-gate bipolar transistor, and wherein themonitored characteristic comprises a forward volt drop of the IGBT andthe predetermined threshold is met based on the forward volt dropreaching a threshold voltage.
 10. The method of claim 9, wherein themonitored characteristic comprises a junction temperature of the IGBT,and the predetermined threshold is met based on the junction temperaturereaching a threshold temperature comprising 150 degrees Celsius.
 11. Themethod of claim 9, further comprising: indicating that the monitoredcharacteristic has met the predetermined threshold via a display, an LEDindicator or a communication mechanism structured to communicate with anexternal device.
 12. The method of claim 11, further comprising:notifying a user that the solid state switch needs to be serviced orreplaced.